Color filter array and manufacturing method thereof

ABSTRACT

A color filter array for an image sensing device is disclosed. The color filter array includes a plurality of pixels and a control unit. The plurality of pixels is utilized for generating a plurality of pixel data of an image. The control unit is utilized for controlling the plurality of pixels. In addition, each of the plurality of pixels is divided into a plurality of sub-pixels corresponding to the same color. When outputting the plurality of pixel data, each of the plurality of pixels accumulates pixel value of at least one of the plurality of sub-pixels in each of the plurality of pixels as the pixel data outputted by each of the plurality of pixels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a color filter array for an imagesensing device and manufacturing method thereof, and more particularly,to a color filter array capable of enlarging a dynamic range of an imagesensing device and the manufacturing method thereof.

2. Description of the Prior Art

Image sensing devices are widely utilized in digital electronicproducts, such as scanners, digital cameras, mobile phones and personaldigital assistants. The most common types of image sensing device areComplementary Metal Oxide Semiconductors (CMOS) and Charge CoupledDevice (CCD). These image sensing devices are both silicon semiconductordevices utilized for sensing light and transferring the sensed lightinto electricity. The electricity generated by the image sensing deviceis transferred into measureable voltages, from which digital data can beacquired.

Please refer to FIG. 1, which is a characteristic diagram of theluminous flux received by a conventional image sensing device and thevoltage generated by the conventional image sensing device. The voltagecorresponds to the image information sensed by the image sensing device.As shown in FIG. 1, the image sensing device transfers the luminous fluxto a measureable voltage once the luminous flux received by the imagesensing device exceeds a minimum luminous flux LFmin. In other words,the image sensing device acquires valid image information when theluminous flux received by the image sensing device during an imagesensing time period exceeds the minimum luminous flux LFmin. Thus, ifthe minimum luminous flux is made smaller, the image sensing device mayacquire image information corresponding to less luminance.

The image sensing generates a maximum voltage Vmax when the luminousflux received by the image sensing device exceeds a maximum luminousflux LFmax. In other words, the image sensing device outputs maximumvoltage Vmax when different image information having correspondingluminous flux exceeding the maximum luminous flux LFmax are received bythe image sensing device. In such a condition, the different imageinformation cannot be identified. Therefore, when the maximum luminousflux LFmax becomes higher, the luminous flux range of the imageinformation which can be identified by the image sensing device becomesbroader. The prior art provides a dynamic range (DR) as an indicator forevaluating the luminous flux range of the image information which iscapable of being identified by the image sensing device, i.e. the rangeof the luminous flux which is received by the image sensing device andis capable of being identified by the image sensing device. The dynamicrange is defined as:

${D\; R} = {20\;{{Log}\left( \frac{L\; F\;\max}{L\; F\;\min} \right)}}$

Generally, when the dynamic range of the image sensing device increases,the luminance differences in the image information which can be sensedby the image sensing device become greater. Thus, how to increase thedynamic range of the image sensing device becomes a topic to bediscussed.

SUMMARY OF THE INVENTION

In order to solve the above problem, the present invention provides acolor filter array capable of enlarging a dynamic range of an imagesensing device and the manufacturing method thereof.

In an aspect, the present invention discloses a color filter array foran image sensing device. The color filter array comprises a plurality ofpixels and a control unit. The plurality of pixels is utilized forgenerating a plurality of pixel data of an image. The control unit isutilized for controlling the plurality of pixels. In addition, each ofthe plurality of pixels is divided into a plurality of sub-pixelscorresponding to the same color. When outputting the plurality of pixeldata, each of the plurality of pixels accumulates pixel value of atleast one of the plurality of sub-pixels in each of the plurality ofpixels as the pixel data outputted by each of the plurality of pixels.The dynamic range of the color filter array is therefore enlarged.

As to another aspect, the present invention discloses a method ofmanufacturing a color filter array, which is used for generating aplurality of pixel data of an image. The method comprises arranging arepeated pattern, repeatedly, for forming a color filter arraycomprising a plurality of pixels; and dividing each of the plurality ofpixels into a plurality of sub-pixels with the same pixel color. Whenoutputting the plurality of pixel data, each of the plurality of pixelsaccumulates pixel value of at least one of the plurality of sub-pixelsin each of the plurality of pixels as the pixel data outputted by eachof the plurality of pixels. The dynamic range of the color filter arraymanufactured by the method can be effectively enlarged.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a characteristic diagram of the luminous flux received by aconventional image sensing device and the voltage generated by theconventional image sensing device.

FIG. 2 is a schematic diagram of an image sensing device according to anexample of the present invention.

FIG. 3 is a schematic diagram of a repeated pattern in the color filterarray of the image sensing device shown in FIG. 2.

FIG. 4 is a schematic diagram of another repeated pattern in the colorfilter array of the image sensing device shown in FIG. 2.

FIGS. 5A and 5B are schematic diagrams of pixels in the color filterarray of the image sensing device shown in FIG. 2.

FIG. 6 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

In the following examples, each pixel of a color filter array in animage sensing device is divided into a plurality of sub-pixels. When theimage sensing device captures an image, each pixel acquires pixel dataof the pixel in the image via accumulating a pixel value of at least oneof the plurality of sub-pixels, so as to increase a dynamic range of theimage sensing device.

Please refer to FIG. 2, which is a schematic diagram of an image sensingdevice 20 according to an example of the present invention. The imagesensing device may be an electronic product with an image sensingfunction, such as a digital camera, a digital video camera or a smartphone. As shown in FIG. 2, the image sensing device 20 comprises animage sensing module 200 and a computing module 202. The image sensingmodule 200 comprises a timing control unit 204, a row selecting unit206, a column sampling unit 208 and a color filter array 210, and isutilized for capturing pixel data PD11-PDij of an image IMG according toa control signal CON. The color pixel array 210 comprises pixels P11-Pijand the computing module 202 is utilized for generating the controlsignal CON to control the image sensing module 200 and for processingthe pixel data PD11-PDij to generate the image IMG. Note that, each ofthe pixels P11-Pij is divided into a plurality of sub-pixels SP1-SPx(FIG. 2 takes the pixel P11 as an example). The color filter array 210may adjust the outputted pixel data PD11-PDij according to pixel valuessensed by each of the plurality of sub-pixels SP1-SPx in each of thepixels P11-Pij. As a result, the dynamic range of the image sensingdevice 20 is effectively increased.

In detail, a pixel Pnm of the pixels P11-Pij may generate the maximumvoltage Vmax corresponding to a pixel value 255 (e.g. a digital value255) when the pixel Pnm receives the maximum luminous flux LFmax and isnot divided into the plurality of sub-pixels SP1-SPx. Since the numberof electrons in the pixel Pnm is saturated when the pixel Pnm receivesthe maximum luminous flux LFmax, the pixel Pnm still generates themaximum voltage Vmax even if the luminous flux received by the pixel Pnmexceeds the maximum luminous flux LFmax. For example, the pixel Pnmwould generate the maximum voltage Vmax corresponding to the pixel value255 when the pixel Pnm receives the luminous flux

$\frac{3}{2}L\; F\;{\max.}$Under such a condition, the pixel Pnm cannot present the real luminancedifferences between the pixels P11-Pij.

In this example, the pixel Pnm is divided into the plurality sub-pixelsSP1-SPx which are corresponding to the pixel color of the pixel Pnm.When the pixel Pnm receives the luminous flux

${\frac{3}{2}L\; F\;\max},$each of the sub-pixels SP1-SPx receives the luminous flux

$\frac{3}{2x}L\; F\;\max$and the voltages generated by each of the sub-pixels SP1-SPx iscorresponding to the pixel value

$\frac{3}{2x} \times 255.$Since the number of the sub-pixels SP1-SPx is greater than or equal to2, the pixel value

$\frac{3}{2x} \times 255$must be smaller than the pixel value 255. In such a condition, the pixelPnm may accumulate the pixel value

$\frac{3}{2x} \times 255$of at least one of the sub-pixel SP1-SPx as the outputted pixel dataPDnm. For example, the pixel Pnm may acquire the pixel value

$\frac{3}{2x} \times 255$of one of the sub-pixels SP1-SPx as the pixel data PDnm. Or, thedesigner may define a saturated threshold TH and limit the pixel dataPDnm outputted by the pixel Pnm to be smaller than or equal to thesaturated threshold TH. In an example, the saturated threshold may bethe pixel value 255. As long as the pixel data PDnm does not exceed thepixel value 255, the pixel Pnm may accumulate the pixel values of randomnumber of the sub-pixels SP1-SPx as the pixel data PDnm. As a result,the dynamic range of the image sensing device 20 can be increased.

Please refer to FIG. 3, which is a repeated pattern RP1 of the colorfilter array 210 shown in FIG. 2. The color filter array 210 can berealized by repeatedly arranging the repeated pattern RP1. Note that,FIG. 3 is utilized for illustrating the relative positions among thepixels and is not utilized for limiting the actual length-width ratio ofeach pixel. As shown in FIG. 3, the repeated pattern RP1 comprisespixels P1-P4, wherein the pixels P1-P4 may be the adjacent pixels amongthe pixels P11-Pij shown in FIG. 2. The pixel P2 is adjacent to theright side of the pixel P1, the pixel P3 is adjacent to the bottom sideof the pixel P1 and the pixel P4 is adjacent to the pixels P2 and P3.The pixels P1-P4 are corresponding to red, green, green and blue,respectively.

Further, the pixels P1-P4 of the repeated pattern RP1 are respectivelydivided into sub-pixels SP1_1-SP1_4, SP2_1-SP2_4, SP3_1-SP3_4 andSP4_1-SP4_4, wherein the sub-pixels SP1_1-SP1_4 are corresponding to redof the pixel P1, the sub-pixels SP2_1-SP2_4 are corresponding to greenof the pixel P2, and so on. In such a condition, the pixels P1-P4 mayadjust the outputted pixel data according to the pixel values sensed bythe sub-pixels SP1_1-SP1_4, SP2_1-SP2_4, SP3_1-SP3_4 and SP4_1-SP4_4.

In an example, the pixel P1 is not divided into the plurality ofsub-pixels SP1_1-SP1_4 and may generate the maximum voltage Vmaxcorresponding to the pixel value 255 when the pixel P1 receives themaximum luminous flux LFmax. The pixel P1 still generates the maximumvoltage Vmax even if the luminous flux received by the pixel P1 exceedsthe maximum luminous flux LFmax. For example, the pixel P1 wouldgenerate the maximum voltage Vmax corresponding to the pixel value 255when the pixel Pnm receives the luminous flux

$\frac{4}{3}L\; F\;{\max.}$Under such a condition, the pixel P1 cannot present the actual luminancedifferences among the pixels P1-P4.

In comparison, the pixel P1 is divided into the sub-pixels SP1_1-SP1_4in this example. Each of the sub-pixels SP1_1-SP1_4 receives theluminous flux when the pixel P1 receives the luminous flux

$\frac{1}{3}L\; F\;{\max.}$In such a condition, each of the sub-pixels SP1_1-SP1_4 generates avoltage

$\frac{1}{3}V\;\max$corresponding to the pixel value 85. The pixel P1 may accumulate thepixel values of 1-3 of the sub-pixels SP1_1-SP1_4 as the outputted pixeldata. For example, the pixel P1 may acquire the pixel value 85 of one ofthe sub-pixels SP1_1-SP1_4 as the outputted pixel data. Or, the pixel P1may accumulate the pixel values of 2 of the sub-pixels SP1_1-SP1_4 andacquire the pixel value 170 as the outputted pixel data. Further, thepixel P1 may accumulate the pixel values of 3 of the sub-pixelsSP1_1-SP1_4 and acquire the pixel value 255 as the outputted pixel data.That is, the saturated threshold TH is defined as the pixel value 255corresponding to the maximum voltage Vmax in this example. According tothe above descriptions, the color filter array 210 realized byrepeatedly arranging the repeated pattern RP1 effectively improves thedynamic range of the image sensing device 20.

In the above example, the sensitivity of the color filter array 210 maybe decreased by dividing each pixel of the color filter array 210 intothe plurality of sub-pixels SP1-SPx. In an example, the sensitivity ofthe color filter array can be improved via altering parts of thesub-pixels SP1-SPx of each pixel to be corresponding to another pixelcolor (e.g. white). Please refer to FIG. 4, which is schematic diagramof a repeated pattern RP2 in the color filter array 210 shown in FIG. 2.The repeated pattern RP2 shown in FIG. 4 is similar to the repeatedpattern RP1 shown in FIG. 3, thus the components with similar functionsuse the same symbols. Different from the repeated pattern RP1 shown inFIG. 3, the sub-pixels SP2_1, SP2_2, SP2_4, SP3_1, SP3_3, SP3_4 arechanged to be corresponding to white. Under such a condition, thesub-pixels SP2_1, SP2_2, SP2_4, SP3_1, SP3_3, SP3_4 can receive moreluminous flux and the sensitivity of the color filter array 210 istherefore increased.

The above examples divide each pixel of the color filter array in theimage sensing device into the plurality of sub-pixels and accumulate thepixel value of at least one of the plurality of sub-pixels in each pixelas the pixel data, to increase the dynamic range of the image sensingdevice. According to different applications and design concepts, thosewith ordinary skill in the art may observe appropriate alternations andmodifications. For example, the ratio between a number of whitesub-pixels and that of green sub-pixels in the pixels P2 and P3 shown inFIG. 4 may be changed to 1, and is not limited herein. In anotherexample, the sub-pixels corresponding to red and blue may alter to becorresponding to white, so as to improve the sensitivity of the colorfilter array 210. Moreover, parts of the sub-pixels in the color filterarray 210 may change to other appropriate colors (e.g. yellow), whichare different from red, blue, green and white, and the sensitivity ofthe color filter array 210 can be also improved.

In addition, the method of dividing the pixel into the plurality ofsub-pixels is not limited to those shown in FIGS. 3 and 4. Please referto FIG. 5A and 5B, which are schematic diagrams of pixels in the colorfilter array 210 shown in FIG. 2. In FIG. 5A, a pixel P5 is divided intosub-pixels SP5_1-SP5_y which are arranged as a strip. As shown in FIG.5B, a pixel P6 is divided into sub-pixels SP6_11-SP6_2z which arearranged as a rectangle. According to different design concepts, themethod of dividing the pixel into the plurality of sub-pixels can beappropriately altered and modified.

The method of realizing the color filter array 210 shown in FIG. 2 canbe summarized into a process 60 as shown in FIG. 6. The process 60 maybe utilized for manufacturing a color filter array used in the imagesensing device. The color filter array manufactured through the process60 inherently has a great dynamic range. The process 60 comprises thefollowing steps:

Step 600: Start.

Step 602: Arrange a repeated pattern, repeatedly, to form a color filterarray.

Step 604: Divide each pixel of the color filter array into a pluralityof sub-pixels.

Step 606: End.

According to the process 60, each pixel of the color filter array isdivided into a plurality of sub-pixels. In such a condition, each pixelcan adjust outputted pixel data according to pixel values sensed by thesub-pixels when the color filter array generates the pixel data of animage, to increase the dynamic range of the image sensing device. Thedetailed operations of the process 60 can be referred to the above andare not narrated herein for brevity.

To sum up, the above examples divide each pixel of the color filterarray in the image sensing device into a plurality of sub-pixels andaccumulate the pixel value of at least one of the plurality ofsub-pixels in each pixel as the pixel data. The dynamic range of theimage sensing device is effectively increased, therefore.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A color filter array for an image sensing device,the color filter array comprising: a plurality of pixels, for generatinga plurality of pixel data of an image; and a control unit, forcontrolling the plurality of pixels; wherein each of the plurality ofpixels is divided into a plurality of sub-pixels corresponding to thesame color; wherein each of the plurality of pixels accumulates pixelvalue of at least one of the plurality of sub-pixels in each of theplurality of pixels as the pixel data outputted by each of the pluralityof pixels; wherein the plurality of sub-pixels in a first pixel of theplurality of pixel is corresponding to a first pixel color, and at leastone of the plurality of sub-pixels in the first pixel is altered to becorresponding to a second pixel color; wherein the first color isdifferent from the second pixel color.
 2. The color filter array ofclaim 1, wherein the pixel data outputted by each of the plurality ofpixels is smaller than a saturated threshold.
 3. The color filter arrayof claim 1, wherein the second pixel color is white.
 4. The color filterarray of claim 1, wherein the plurality of sub-pixels in each pixel isarranged as a strip.
 5. The color filter array of claim 1, wherein theplurality of sub-pixels in each pixel is arranged as a rectangle.
 6. Thecolor filter array of claim 1 further comprising: a plurality ofrepeated pattern, wherein each of the plurality of repeated patterncomprises a first pixel, a second pixel, a third pixel and a fourthpixel of the plurality of pixels; wherein the second pixel is adjacentto a first side of the first pixel, the third pixel is adjacent to asecond side of the first pixel and the fourth side is adjacent to thesecond pixel and the third pixel; wherein the first pixel, the secondpixel, the third pixel and the fourth pixel are respectivelycorresponding to a first pixel color, a second pixel color, the secondpixel color and a third pixel color.
 7. The color filter array of claim6, wherein the first pixel color, the second pixel color and the thirdpixel color are red, green and blue, respectively.
 8. A method ofmanufacturing a color filter array, which is used for generating aplurality of pixel data of an image, the method comprising: arranging arepeated pattern, repeatedly, for forming a color filter arraycomprising a plurality of pixels; dividing each of the plurality ofpixels into a plurality of sub-pixels with the same pixel color; andaltering at least one of the sub-pixels corresponding to a first pixelcolor in a first pixel of the plurality of pixel to a second pixelcolor; wherein each of the plurality of pixels accumulates pixel valueof at least one of the plurality of sub-pixels in each of the pluralityof pixels as the pixel data outputted by each of the plurality ofpixels; wherein the first pixel color is different from the second pixelcolor.
 9. The method of claim 8, wherein the pixel data outputted byeach pixel is smaller than a saturated threshold.
 10. The method ofclaim 8, wherein the second color is white.
 11. The method of claim 8,wherein the plurality of sub-pixels of each of the plurality of pixelsis arranged as a strip.
 12. The method of claim 8, wherein the pluralityof sub-pixels of each of the plurality of pixels is arranged as arectangle.
 13. The method of claim 8, wherein each of the plurality ofrepeated pattern comprises a first pixel, a second pixel, a third pixeland a fourth pixel of the plurality of pixels; wherein the second pixelis adjacent to a first side of the first pixel, the third pixel isadjacent to a second side of the first pixel and the fourth side isadjacent to the second pixel and the third pixel; wherein the firstpixel, the second pixel, the third pixel and the fourth pixel arerespectively corresponding to a first pixel color, a second pixel color,the second pixel color and a third pixel color.
 14. The method of claim13, wherein the first pixel color, the second pixel color and the thirdpixel color are red, green and blue, respectively.